Micro-electromechanical systems (MEMS) include small mechanical devices performing electrical and mechanical functions that are fabricated using photo-lithography techniques similar to techniques used to fabricate integrated circuits. Some MEMS devices are sensors that can detect motion such as an accelerometer or detect angular rate such as a gyroscope. An accelerometer is a device that undergoes a measurable change in response to acceleration acting on the device. MEMS accelerometers can include piezoelectric, piezoresistive, and capacitive accelerometers. Because of their small size, MEMS sensors are being incorporated into electronic devices such as video game controllers and smart phones.
Capacitive accelerometers undergo a change in capacitance in response to acceleration. Sensing circuits are used to sense the change in capacitance of the MEMS sensor. The design of these sensing circuits poses challenges to reduce noise and minimize size.